\documentclass{article}
\newcommand{\tabincell}[2]{
	\begin{tabular}{@{}#1@{}}#2\end{tabular}
}
\begin{document}
\begin{table}[ht!]
	\label{verilog}
	\caption{Verilog HDL}
	\hspace{0.5cm}
	\centering
	\begin{tabular} {l | l}
		\hline\hline
		hello & \tabincell{c}{ we have implemented a traffic generator where\\ the flow sizes follow the Pareto distribution\\ and the intervals between adjacent packets\\ follow the Poisson distribution}\\
		\hline
	\end{tabular}
\end{table}
\end{document}
